This invention generally relates to techniques for truing and dressing grinding wheels, and is particularly concerned with both a device and method that trues and dresses a grinding wheel with a constant force in order to protract the life span of the dressing roll, and to improve the accuracy of the truing operation.
Devices for truing and dressing grinding wheels are well known in the prior art. In the grinding arts a "truing" operation is performed on a grinding wheel in order to insure that the profile of its peripheral work surface is cut to a proper shape and is also concentric at all points with the axis of rotation of the wheel. By contrast, a "dressing" operation creates the desired abrasive condition on the surface of the grinding wheel. Truing and dressing operations are often performed on both newly manufactured and used grinding wheels to initiate and maintain a desired profile and proper surface conditions on the wheel. The truing operation properly shapes the wheel by grinding away a portion of the peripheral surface of the wheel in accordance with a pattern, while the dressing operation removes some of the bonding agent that surrounds the particles of abrasive material from the wheel surface, thereby exposing more of the sharp edges of these abrasive particles to better cut a workpiece.
In prior art truing and dressing operations, the grinding wheel is rotated while a truing and dressing tool is engaged against its outer periphery. In order to be effective, the truing and dressing tool must be formed from an abrasive material that is harder than the abrasive used in the grinding wheel. The grinding wheel, in turn, must be formed from abrasive materials that are harder than the material forming the workpiece. Because of the ever increasing demand for workpieces formed from ever harder work materials, there is an increasing use of truing and dressing tools that employ only the very hardest abrasive materials, i.e., diamond or CBN. Unfortunately, diamond and CBN truing and dressing tools are quite expensive. A single diamond roll used in such a tool costs approximately $6,000.00. Worst yet, the applicant has observed that the life span of such a diamond roll has been substantially shortened when the roll is used to true and dress the harder grinding wheels which are employed more and more to machine the much demanded harder workpieces. For example, while such a diamond roll could perform truing and dressing operations on conventional fused aluminum oxide grinding wheels for up to a year, its life time is attenuated to only one or two months when the same roll is used to true and dress harder silicon carbide and sol-gel aluminum oxide grinding wheels. The short life span of the diamond truing and dressing roll not only increases the cost of the shaping and machining operation on the workpieces, but also substantially increases downtime at the factory. Moreover, the use of harder grinding wheels has also increased the time necessary for satisfactorily completing a truing and dressing operation to acceptable tolerances, which again increases the downtime and expense associated with the grinding operation.
Clearly, there is a need for a device and method for truing and dressing grinding wheels employing hard abrasives which increases the life span of the diamond roll used in the truing and dressing tools. Ideally, such a device should reduce the time necessary for satisfactorily completing a truing and dressing operation so as to minimize downtime. Finally, it would be desirable if such a device and technique were capable of truing and dressing such hard grinding wheels with a high degree of precision to enable the wheels to shape and machine their respective workpieces to tight tolerances.